In gasoline engines knocking may be detected by a knock sensor. This knock sensor is disposed on the gasoline engine and conveys solid-borne sound vibrations of the gasoline engine, which occur as a result of explosion-like combustion events inside the cylinder of the gasoline engine, to an evaluation unit. These explosion-like combustion events occurring inside the combustion chamber of the gasoline engine are converted into vibrations that are conveyed to the walls of the internal combustion engine and are perceived there as solid-borne sound.
Present-day knock recognition is based on integration of the filtered and rectified solid-borne sound signals and the reference levels calculated therefrom. Integration occurs over the knock-relevant time region. This method is based substantially on methods of linear system theory and signal processing. The reference variable for knock recognition is the peak value of the bandpass-filtered cylinder pressure signal.
The same evaluation strategy is used for pre-ignition recognition. The reference variable for this combustion anomaly is the maximum value of the unfiltered cylinder pressure signal. A third example of a combustion anomaly that can be recited is misfire recognition. This event is likewise evaluated using methods from the field of system theory and signal processing, although they are utilized to evaluate a sensor information item of a crankshaft transducer.
It is disadvantageous that despite complex evaluation methods, reliable recognition of every type of abnormal combustion process under all operating conditions cannot always be guaranteed. In addition, large calculation capacities in control units of the motor vehicle extend the execution times of these evaluation methods.